This invention relates to dynamoelectric machine wire wound stators and particularly to polyphase multi-pole wire wound stators having common neutral wire connections.
In polyphase machines, for example AC induction motors, commonplace stator winding arrangements include groupings of two-terminal coils wherein, for each grouping, one terminal of each coil is a respective voltage phase input terminal (phase terminal) and the other terminals of all coils are commonly coupled and referred to as the neutral connection. For example, in a three phase AC induction motor one grouping consists of three two-terminal coils, one for each phase A, B and C. The three coils are commonly coupled at one respective terminal thereof to form the neutral connection leaving the respective other phase terminals independent one from the other to receive one of the three mutually exclusive phase voltages. This arrangement of coils is commonly referred to as a Y-connection for obvious reasons. Each Y-connection therefore is a grouping of coils as described.
Commonly, an AC induction motor has a plurality of such coil groupings with respective like phase terminals thereof coupled together to operate off of the same input voltage phase and the plurality of individual neutral connections further being commonly coupled one to the other.
Such multiple grouping stator windings are fairly cumbersome in their manufacture. For example, in a common three phase, four pole AC induction motor, twelve individual coils are required. This means that twelve coil terminals, one terminal from each coil, are commonly coupled as a neutral connection. A variety of methods are practiced to accomplish this task, among them being wire splicing, electrical clips, soldering, brazing and combinations thereof. Such joining methods require insulation of such coupling joints to prevent shorting to other portions of the stator windings and/or, since the neutral is floating, to the stator and/or motor housing structures. This method of assembly is labor intensive, not readily adapted to automated manufacturing and subject to excessive variability and questionable durability.